gc: destructors is beginning to work (#10483)

* kochdocs.nim: code cleanup
* docgen: nicer indentation
* parser.nim: code cleanup
* fixes #10458
* make tests green again
* make =destroy mixins
* gc:destructors: produced C code is almost working
* --gc:destructors simple program compiles (but leaks memory)
* gc:destructors make examples compile in C++ mode
* destructors: string implementation bugfixes
* strs.nim: minor code cleanup
* destructors: builtin seqs are beginning to work
* remove debugging helpers

compiler/cgen.nim

@@ -264,6 +264,12 @@ proc addrLoc(conf: ConfigRef; a: TLoc): Rope =
   if lfIndirect notin a.flags and mapType(conf, a.t) != ctArray:
     result = "(&" & result & ")"
 
+proc byRefLoc(p: BProc; a: TLoc): Rope =
+  result = a.r
+  if lfIndirect notin a.flags and mapType(p.config, a.t) != ctArray and not
+      p.module.compileToCpp:
+    result = "(&" & result & ")"
+
 proc rdCharLoc(a: TLoc): Rope =
   # read a location that may need a char-cast:
   result = rdLoc(a)